Explanation:
The largest of its kind, the
High
Energy Stereoscopic System (H.E.S.S.) II telescope stands in the
foreground of this photo.
Tilted horizontally it reflects the inverted landscape of
the Namibian desert in a segmented mirror 24 meters wide and
32 meters tall, equal in area to two tennis courts.
Now beginning an
exploration of the Universe at extreme energies,
H.E.S.S. II saw first light on July 26.
Most ground-based telescopes with lenses and mirrors are hindered by
the Earth's nurturing, protective
atmosphere that blurs images and
scatters and absorbs light.
But the H.E.S.S. II telescope is a cherenkov telescope, designed to
detect gamma rays - photons with
over 100 billion times the energy of visible
light - and actually requires the atmosphere to operate.
As the gamma rays impact
the upper atmosphere they produce air
showers of high-energy particles.
A large camera
at the mirror's focus records in detail
the brief flashes of optical light, called
cherenkov light,
created by the air shower particles.
The H.E.S.S. II telescope operates in concert
with the array of four other 12 meter cherenkov
telescopes to provide multiple stereoscopic views of the air showers,
relating them to the energies and directions of the incoming
cosmic gamma rays.